Iron (Fe), a crucial component of the Earth's biogeochemical cycle, has a significant impact on global ecology and carbon cycling. Understanding the effect of Fe on the carbon cycle is essential for comprehending biogeochemical processes of carbon and climate change. 

The traditional view suggests that dissimilatory iron reduction (DIR) can drive the release of organic carbon (OC) as carbon dioxide (CO₂) by mediating electron transfer between organic compounds and microbes. However, it is important to note that this view may be subjective and requires further investigation to confirm its validity. 

A recent study led by Prof. XING Peng from the Nanjing Institute of Geography and Limnology, Chinese Academy Sciences, found that dissolved inorganic carbon (DIC) was crucial for carbon sequestration. DIC affected inorganic-carbon redistribution via iron abiotic-phase transformation. The study was published in Global Change Biology on 18 March. 

The study discovered that the abiotic and biotic processes at the organic carbon-microbe-mineral interface facilitated CO₂ sequestration and reduced its emission by half. The redistribution of inorganic carbon within or among the atmosphere, lithosphere, and hydrosphere is critical for the fate of elevated CO₂. 

Additionally, researchers found that high porosity promoted electron transport and DIR bacteria activity, which can increase the rate of iron reduction. The presence of iron, calcium, and organic carbon in the environment can create a porous sediment structure that facilitates rapid DIR. This environment is conducive to the formation and growth of iron minerals that contain carbonate (ICFe), which can sequester inorganic carbon. The researchers also found that a minimum DIR threshold of 6.65 μmol g^-1 dw day^-1 was necessary for ICFe formation. 

 The 'OC-microbe-mineral reactions' involved both biotic and abiotic reactions, which improve our understanding of the processes that mediate CO₂ sequestration in anoxic subsurface environments such as soils, wetlands, and sediments. Furthermore, modelling studies suggested that microbial iron reduction was more thermodynamically favorable under elevated CO₂, which could mitigate the negative impact of elevated CO₂ on global warming. 

 "The information can help assess the sequestration of DIC resulting from both abiotic and biotic processes working together. It is also useful for monitoring and managing CO₂ sequestration, as well as developing appropriate engineering strategies to remediate CO₂ sequestration in these environments," said Prof. XING Peng, corresponding author of the study.